Audio Drift when Exporting Premiere Pro

I'm working with multiple mp4 files at constant frame rates (24 fps). Each video file has wav audio as well, and the project is perfectly in sync throughout the project in the preview frame. Unfortunately on export there's a noticeable drift of 0.5-1.5 seconds by the time the video concludes (~45 min video). This has now happened to me twice. 

I'm on a new Mac Mini (M1 chip) in Premiere Pro Beta. 

I see others have had this issue but it seems to be because they're working with VFR video files--mine are CFR. Any other ideas?